HomeRadiologyVol. 243, No. 3 PreviousNext Reviews and CommentaryEditorialsWhat We Do Not Yet Know in the Radiologic SciencesBrian C. Lentle, Roberta E. Arnold, Gary J. Becker, R. Nick Bryan, Peggy J. Fritzsche, David H. HusseyBrian C. Lentle, Roberta E. Arnold, Gary J. Becker, R. Nick Bryan, Peggy J. Fritzsche, David H. HusseyAuthor Affiliations1From the Radiological Society of North America, 820 Jorie Blvd, Oak Brook, IL 60523. Received January 5, 2007; final version accepted January 8.Address correspondence to B.C.L. (e-mail: [email protected]).Brian C. LentleRoberta E. ArnoldGary J. BeckerR. Nick BryanPeggy J. FritzscheDavid H. HusseyPublished Online:Jun 1 2007https://doi.org/10.1148/radiol.2433070028MoreSectionsFull textPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In References1 Thomas L. The youngest science: notes of a medicine watcher. New York, NY: Viking, 1983. Google Scholar2 Looking back on the millennium in medicine. N Engl J Med 2000;342:42–49. Crossref, Medline, Google Scholar3 Kennedy D, Norman C. What don't we know? Science 2005;309:75. Google Scholar4 Siegfried T. In praise of hard questions. Science 2005;309:76–77. Crossref, Medline, Google Scholar5 Maddox J. What remains to be discovered. New York, NY: The Free Press (Simon & Schuster), 1998. Google Scholar6 Lord Kelvin quotations. http://www.zapatopi.net/kelvin/quotes. Accessed December 1, 2006. Google Scholar7 Smolin L. Why no “new Einstein”? Physics Today 2005;58:56. Google Scholar8 Alfonso X of Castile. Answers.com. http://www.answers.com/topic/alfonso-x-of-castile. Accessed December 1, 2006. Google ScholarArticle HistoryPublished in print: 2007 FiguresReferencesRelatedDetailsRecommended Articles Impact of COVID-19 on Clinical Care and Research in Cancer Imaging: Where We Are NowRadiology: Imaging Cancer2021Volume: 3Issue: 1Celebrating Contributions of Imaging Technology to Fight against Cancer at the 50th NCA AnniversaryRadiology: Imaging Cancer2022Volume: 4Issue: 5PET/MRI for Primary Breast Cancer: A Match Made Better by PET Quantification?Radiology: Imaging Cancer2021Volume: 3Issue: 1Nanotechnology for Cancer Imaging: Advances, Challenges, and Clinical OpportunitiesRadiology: Imaging Cancer2021Volume: 3Issue: 3Radiology and Technology: Where We’ve Been, Where We’re Going—And Why I Am So ExcitedRadiology: Artificial Intelligence2020Volume: 2Issue: 3See More RSNA Education Exhibits Current Applications of PET/MR Imaging for Evaluation of Pediatric Musculoskeletal DiseaseDigital Posters2022Current Status and Future Prospects in Radioligand TherapyDigital Posters2020A Grassroots Approach To Forming A Diversity, Equity, And Inclusion Committee In An Academic Radiology Department: Early Successes And Lessons LearnedDigital Posters2021 RSNA Case Collection Bing-Neel syndromeRSNA Case Collection2021Dedifferentiated Thyroid CancerRSNA Case Collection2020Bilateral ParagangliomasRSNA Case Collection2022 Vol. 243, No. 3 Metrics Altmetric Score PDF download

HomeRadiologyVol. 224, No. 2 PreviousNext Special CommunicationThe Radiological Society of North America 88th Scientific Assembly and Annual Meeting Sunday, December 1 to Friday, December 6, 2002, McCormick Place, Chicago, IllinoisR. Nick BryanR. Nick BryanAuthor Affiliations1In accordance with the bylaws of the Radiological Society of North America (section 6.12), the Board of Directors has appointed a Committee on Nominations. In 2002, the Committee on Nominations consists of Peggy J. Fritzsche, MD, Chairman, Riverside, Calif; Jerry P. Petasnick, MD, Chicago, Ill; and Glenn Forbes, MD, LaCrosse, Wisc. Suggestions for nominations should be addressed to the Chairman.R. Nick BryanPublished Online:Aug 1 2002https://doi.org/10.1148/radiol.2242022526MoreSectionsFull textPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: Aug 2002 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 224, No. 2 Metrics Altmetric Score PDF download

HomeRadiologyVol. 210, No. 1 PreviousNext Special CommunicationWilliam W. Olmsted, MD, New RSNA Education EditorJerry P. Petasnick1, R. Nick Bryan1Jerry P. Petasnick1, R. Nick Bryan1Author AffiliationsRadiological Society of North America, 820 Jorie Blvd, Oak Brook, IL 60523.Jerry P. Petasnick1R. Nick Bryan1Published Online:Jan 1 1999https://doi.org/10.1148/radiology.210.1.r99ja6536MoreSectionsFull textPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: Jan 1999 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 210, No. 1 Metrics Altmetric Score PDF download

OBJECTIVES:The aim of this study was to determine accuracy of transcranial Doppler ultrasound (TCD) and compare efficacy of three non-invasive tests [TCD, magnetic resonance angiography (MRA), and magnetic resonance imaging (MRI)] in patients with acute cerebral ischemia.MATERIAL AND METHODS:This prospective study involved 30 patients. MRI, MRA, and TCD were performed within 24 h after onset of ictus. The 2nd MRI was repeated at 48-72 h and was used as the standard for the evaluation of sensitivity and specificity of MRA, TCD, and initial MRI.RESULTS:TCD showed a sensitivity of 96% and a specificity of 33% for recognizing abnormal cerebral blood flow velocities. MRA showed a sensitivity of 46% and a specificity of 75% for assessing intracranial vascular anatomy, while initial MRI revealed a sensitivity of 84% and a specificity of 100% for evaluation of ischemic parenchymal changes.CONCLUSION:Our results revealed that TCD is an accurate indicator of blood flow status and correlated well with MRI, MRA abnormalities in acute stroke.

OBJECTIVE:To provide the first comprehensive magnetic resonance imaging (MRI) assessment of brain in a series of patients with Lesch-Nyhan syndrome (LNS), with emphasis on basal ganglia measurements.DESIGN:Routine readings of MRI studies, repeated reading in random order blinded to subject diagnosis, and 3-dimensional volumetric measures of basal ganglia regions.SETTING:The Johns Hopkins Hospital, Baltimore, Md.PATIENTS:Seven patients with LNS who have hypoxanthine guanine phosphoribosyltransferase levels less than 1.6% and characteristic clinical features of the disorder, which include hyperuricemia, cognitive impairment, and dystonic movement disorder, were compared with 7 age-matched control subjects. Five of the 7 patients demonstrated self-injurious behavior. MRI studies were performed using general anesthesia because of the severity of the movement disorder.MAIN OUTCOME MEASURES:Measurement of brain regions from MRI-obtained images.RESULTS:Routine readings described mild cerebral atrophy in 2 of 7 patients, but no caudate or putamen abnormalities were reported. However, on the directed blinded rereading, small caudates were suspected in 5 of 7 cases, and abnormalities in cerebral size and cranium were identified. Volumetric studies of the patients with LNS confirmed a 34% decrease in caudate volume (P<.001), a 17% decrease in total cerebral volume (P<.03), and a 12% decrease in putamen volume (P=.19).CONCLUSIONS:To our knowledge, this is the first demonstration of consistent neuroanatomic abnormalities in LNS. The findings of reduced basal ganglia volume are consistent with the dystonic movement disorder.

HomeRadiologyVol. 206, No. 2 PreviousNext ArticlesRadiology and RadioGraphics Add On-line EditionsR. Nick BryanR. Nick BryanAuthor AffiliationsFrom the Radiological Society of North America, 2021 Spring Road, Suite 600, Oak Brook, IL 60523R. Nick BryanPublished Online:Feb 1 1998https://doi.org/10.1148/radiology.206.2.310MoreSectionsPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: Feb 1998 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 206, No. 2 Metrics Altmetric Score PDF download

PURPOSE:To assess whether magnetic resonance (MR) imaging has replaced other diagnostic imaging modalities in the evaluation of persistent low back pain.MATERIALS AND METHODS:Data on diagnostic imaging use in 2,374 adult patients with persistent low back pain in 1987-1990 were analyzed. Multiple logistic regression was used to estimate the annual adjusted odds of lumbosacral spine radiography, MR imaging, unenhanced computed tomography (CT), or CT myelography use. The national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated.RESULTS:The adjusted odds of performing MR imaging in 1990 relative to 1987 was 3.44 (95% confidence interval, 2.63, 4.51), which reflects an estimated increase from 22 studies per 100 enrollees in 1987 to 75 studies per 100 enrollees in 1990. Use of MR imaging in combination with radiography, unenhanced CT, or CT myelography increased. The additional national cost of diagnostic imaging for persistent low back pain in 1990 relative to 1987 was estimated at $70-$176 million.CONCLUSION:MR imaging was used primarily as an add-on rather than a substitute for other imaging modalities in the evaluation of persistent low back pain. Thus, the volume and cost of diagnostic imaging for persistent low back pain have increased.

STUDY DESIGN:Post hoc analysis of data from the National Low Back Pain Study, a prospective observational multicenter study of patients referred for the evaluation and treatment of persistent low back problems. OBJECTIVE:To identify patient characteristics associated with use of particular diagnostic imaging examinations in patients with persistent low back problems. SUMMARY OF BACKGROUND DATA:The Agency for Health Care Policy and Research clinical practice guidelines on low back problems suggest that the use of particular diagnostic imaging tests for a given patient should be based on specific characteristics of that patient. METHODS:Use of diagnostic imaging examinations in 2,374 patients with persistent low back problems who were enrolled in the National Low Back Pain Study from 1986 to 1991 was analyzed. Stepwise logistic regression was used to identify patient characteristics that distinguish between enrollees who underwent particular imaging studies. RESULTS:Characteristics that distinguished patients who had undergone magnetic resonance imaging from those who had received only lumbo-sacral spine radiographs included higher socioeconomic status, greater resource use in the preceding 12 months, more functional impairment, presence of sciatica, and presence of neurologic signs/symptoms suggestive of nerve root compromise. Suspected soft tissue involvement was characteristic of enrollees who had undergone magnetic resonance imaging, whereas suspected structural involvement characterized patients who received noncontrast computed tomography. Only nonclinical factors, such as higher annual household income, disability compensation, and male gender distinguished enrollees who had undergone both magnetic resonance imaging and computed tomography-myelography from those who received only computed tomography-myelography. CONCLUSION:Particular patient socioeconomic and clinical characteristics are associated with receipt of specific imaging studies in evaluation of persistent low back problems.

BACKGROUND AND PURPOSE:Animal studies have shown that MR diffusion imaging can outline acute ischemic regions before irreversible damage (infarction) occurs. To study evolution of ischemic lesions in humans, it is therefore important to quantify absolute diffusion constants (D values), but quantitation has not been reproducible among different clinics. These problems are explained, and a method for reproducible quantitation is suggested.METHODS:Diffusion-weighted and absolute diffusion images were acquired, and the absolute apparent diffusion constants in three orthogonal spatial directions (Dxx, Dyy, and Dzz) were measured. These were combined to calculate images of the orientation-independent apparent diffusion parameter Dav = 1/3 Trace[D] = 1/3(Dxx + Dyy + Dzz). Values of the individual diffusion constants and Dav were evaluated in 6 patients and 6 normal volunteers.RESULTS:Patient data show that comparison of diffusion constants between contralateral and ipsilateral hemispheres after ischemia may give results varying by more than 100% depending on orientation. Findings in normal-appearing regions containing a mixture of gray and white matter in patients (n = 5) and in normal volunteers (n = 6) show that Dav = (0.92+/-0.11) x 10(-3) mm2/s, with a small intersubject variation, whereas Dxx, Dyy, and Dzz vary strongly. Hemispheric ratios (ipsilateral/contralateral [I/C]) in these subjects were (I/C)Dav = 1.00+/-0.05, (I/C)Dxx = 1.02+/-0.15, (I/C)Dyy = 1.07+/-0.24, and (I/C)Dzz = 0.96+/-0.28. The individual subjects in this group all had an (I/C)Dav within 10% of unity, while the other three ratios showed intersubject variations as large as 100%.CONCLUSIONS:(I/C)Dav ratios are a reliable means to quantitate changes in absolute diffusion constants for the study of stroke evolution independent of tissue orientation, gradient orientation, and diffusion time. The use of these ratios will enable reproducible intersubject and interclinic quantitation.

PURPOSE:To assess the relationship between imaging findings, therapy, and functional outcome in patients with persistent low back pain who are suspected of having herniated nucleus pulposus.MATERIALS AND METHODS:Data collected during a multicenter, longitudinal study were retrospectively analyzed (n = 1,084). Multivariate regression was used to determine the association between imaging findings, therapy, and functional outcome. The patient outcome measure was disability days: the number of days the patient was unable to perform work-related activities.RESULTS:In patients with at least one normal advanced (imaging other than plain radiography) diagnostic study or with an unconfirmed diagnosis of herniated nucleus pulposus, outcome at 2-year follow-up was no better in patients who were treated than in those who were not. In patients with only abnormal advanced imaging results or with a concordant diagnosis based on clinical and imaging findings, outcome was better in patients who underwent surgery than in those treated nonsurgically. Patients with a free fragment, protrusion, or extrusion that was treated surgically had fewer disability days than patients treated nonsurgically.CONCLUSION:Advanced diagnostic imaging studies can play an important role in treatment selection in patients with persistent low back pain who are suspected of having herniated nucleus pulposus.

HomeRadiologyVol. 205, No. 3 Previous ArticlesFarewell to Radiology Editor: Stanley S. Siegelman, MDR. Nick BryanR. Nick BryanAuthor AffiliationsFrom the Radiological Society of North America, 2021 Spring Rd, Suite 600, Oak Brook, IL 60523R. Nick BryanPublished Online:Dec 1 1997https://doi.org/10.1148/radiology.205.3.878MoreSectionsPDF ToolsAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookXLinked In Article HistoryPublished in print: Dec 1997 FiguresReferencesRelatedDetailsRecommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 205, No. 3 Metrics Altmetric Score PDF download

Dopamine (DA) deficiency has been implicated in Lesch-Nyhan disease (LND), a genetic disorder that is characterized by hyperuricemia, choreoathetosis, dystonia, and compulsive self-injury. To establish that DA deficiency is present in LND, the ligand WIN-35,428, which binds to DA transporters, was used to estimate the density of DA-containing neurons in the caudate and putamen of six patients with classic LND. Comparisons were made with 10 control subjects and 3 patients with Rett syndrome. Three methods were used to quantify the binding of the DA transporter so that its density could be estimated by a single dynamic positron emission tomography study. These approaches included the caudate- or putamen-to-cerebellum ratio of ligand at 80-90 min postinjection, kinetic analysis of the binding potential [Bmax/(Kd x Vd)] using the assumption of equal partition coefficients in the striatum and the cerebellum, and graphical analysis of the binding potential. Depending on the method of analysis, a 50-63% reduction of the binding to DA transporters in the caudate, and a 64-75% reduction in the putamen of the LND patients was observed compared to the normal control group. When LND patients were compared to Rett syndrome patients, similar reductions were found in the caudate (53-61%) and putamen (67-72%) in LND patients. Transporter binding in Rett syndrome patients was not significantly different from the normal controls. Finally, volumetric magnetic resonance imaging studies detected a 30% reduction in the caudate volume of LND patients. To ensure that a reduction in the caudate volume would not confound the results, a rigorous partial volume correction of the caudate time activity curve was performed. This correction resulted in an even greater decrease in the caudate-cerebellar ratio in LND patients when contrasted to controls. To our knowledge, these findings provide the first in vivo documentation of a dopaminergic reduction in LND and illustrate the role of positron emission tomography imaging in investigating neurodevelopmental disorders.

PURPOSE:To locate spoiled gradient-echo functional MR signal changes in relation to brain parenchyma.METHODS:The region of the primary visual cortex was evaluated using functional MR and H2 15O positron emission tomography in each of six male subjects who were being visually stimulated by means of red light-emitting diode flash goggles.RESULTS:The positron emission tomography technique demonstrated substantially greater relative signal change with visual stimulation than did the functional MR technique. Furthermore, the functional MR signal changes were concentrated in loci around the periphery of brain parenchyma exhibiting increased radiotracer activity, as opposed to being collocated.CONCLUSIONS:Signal changes found using functional MR based on gradient-echo techniques reflect primarily phenomena occurring within small veins and underrepresent activity intrinsic to brain parenchyma, thus introducing potential inaccuracies in locating regions of activated brain tissue. Positron emission tomography, however, directly measures changes in metabolically related activity within the parenchyma.